The present disclosure relates to a gas turbine engine, and more particularly to an engine having an airflow structure that helps mitigate acoustic response to reduce total effective perceived noise level (EPNL).
Gas turbine engines which have an engine cycle modulated with a variable area fan nozzle (VAFN) provide a smaller fan nozzle exit area during cruise conditions and a larger fan nozzle exit area during take-off and landing conditions. The VAFN may generate noise as upstream turbulence interacts with the VAFN.
Fan exit guide vanes (FEGVs) are disposed in gas turbine engines downstream from a fan to de-swirl circumferentially flowing air discharged from the fan into an axial direction prior to the air flowing into a bypass flow duct. The FEGVs may generate noise as upstream turbulence generated by the fan interacts with the FEGVs.